This invention relates to a method for delaying curing rate of a curable resin composition.
In general, when a resin composition comprising a polyfunctional cyanate ester compound selected from the group consisting of (1) a polyfunctional cyanate ester, a homoprepolymer of one or more cyanate ester of (1) and a coprepolymer of (1) and an amine (sometimes hereinunder referred to as polyfunctional cyanate ester compound), the polyfunctional cyanate ester compound and a polyfunctional maleimide compound selected from the group consisting of (1) a polyfunctional maleimide, a homoprepolymer of (1) and a coprepolymer of (1) and an amine (sometimes hereinunder referred to as polyfunctional maleimide compound) are merely heated, the composition gives rise to gelation, whereby the composition is cured. Gelation rate or curing rate of the composition is accelerated by adding a catalyst, such as a tertiary amine, an imidazole or an organic metal salt to the composition.
In order to obtain gelation rate or curing rate of a curable resin composition suitable for its use or production of cured product in the prior art, amount of catalyst added to the composition has been adjusted or a specific catalyst has been selected.
But in this method, a slight change in the amount of the catalyst, the state of its dispersion, the date of manufacture of the starting materials (i.e. polyfunctional cyanate esters and polyfunctional maleimides) or their storage period causes a substantial variation in the gelling or curing rate of the resulting resin composition that is very hard to eliminate completely.